Enlightenment and knowledge · 1781 onward
Kantianism
Overview
A bridge between reason and experience: the mind shapes and structures everything we can know. We do not meet the world raw.
Kant stands between rationalism and empiricism and refuses both victories. The mind does not meet the world raw. Space, time and the basic categories are the forms in which anything can show up for a creature like us. That is why experience has a structure. It is also why he thinks we cannot know things as they are apart from that structure. Reason has a shore.
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In morals he will not ground the law on what you happen to want. An action has moral worth when it is done from duty, on a maxim you could will as a law for everyone. That test is not a vote, and it is not the silver rule. A shareable rule can still use a person. The formula of humanity says the person is an end. The word “merely” does the work: you may work with someone toward a shared aim. You may not treat them as only a tool.
The two sides meet. A mind that structures what it can know is the same mind that can ask what it may do. Kant’s severity is that neither question is answered by a feeling of certainty. The limit on knowledge and the limit on using people are both forms of respect for what is not your instrument.
Where it answers
How do we know?
The mind structures experience. We never meet the world with no form of our own.
What is valid reasoning?
Check the limits of what a mind like ours can even claim to know.
What is beautiful?
Beauty is a judgment we make, and we still expect others to feel its pull.
Key terms
- Categorical imperative
- Act only on a rule you could will everyone to follow, and treat people as ends, never merely as means.
- Phenomena and noumena
- Things as they appear to us, and things as they are in themselves, which we cannot know.
- Synthetic a priori
- Knowledge that tells us something new yet is known without experience, such as 7 + 5 = 12.
- Autonomy
- Giving yourself the moral law through your own reason, rather than taking orders from outside.
In their words
“Act only according to that maxim whereby you can at the same time will that it should become a universal law.”
Further reading
- Critique of Pure Reason · Immanuel Kant
- Groundwork of the Metaphysics of Morals · Immanuel Kant
- Critique of Judgment · Immanuel Kant
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Quest2Reason. “Kantianism.” https://quest2reason.com/learn/ideas/kantianism. Accessed 13 November 2026.